Dysfunctional Rules IX: 1d3 Dysfunctions from the 8th Level List

[Jormengand]

While a fireball can score a critical hit in this circumstance, it doesn't actually do anything - the effect of a normal hit is the fireball passing through the narrow opening, which can't really be doubled.

That's not what a critical hit means:

A critical hit means that you roll your damage more than once, with all your usual bonuses, and add the rolls together.

It multiplies the damage dealt by the attack, not the effect of the attack hitting.